Plasma torch and components thereof

ABSTRACT

Embodiments of the present invention include a plasma cutting torch and plasma cutting torch components, such as electrodes, cathodes, retainer caps, etc. having a unique physical features, including threads relationships. Embodiments include torch components having modified square thread with a specialized thread configuration including a particular relationship between thread crest and root, and included angles of thread sidewalls.

PRIORITY

The present application claims priority to U.S. Provisional ApplicationNo. 62/211,293 filed on Aug. 28, 2015, and U.S. Provisional ApplicationNo. 62/241,077 filed on Oct. 13, 2015, the entire disclosures of whichare fully incorporated herein by reference.

TECHNICAL FIELD

Devices, systems, and methods consistent with the invention relate tocutting, and more specifically to devices, systems and methods relatedto plasma arc cutting torches and components thereof.

BACKGROUND

In many cutting, spraying and welding operations, plasma arc torches areutilized. With these torches a plasma gas jet is emitted into theambient atmosphere at a high temperature. The jets are emitted from anozzle and as they leave the nozzle the jets are highly under-expandedand very focused. However, because of the high temperatures associatedwith the ionized plasma jet many of the components of the torch aresusceptible to failure. This failure can significantly interfere withthe operation of the torch and prevent proper arc ignition at the startof a cutting operation.

Further limitations and disadvantages of conventional, traditional, andproposed approaches will become apparent to one of skill in the art,through comparison of such approaches with embodiments of the presentinvention as set forth in the remainder of the present application withreference to the drawings.

BRIEF SUMMARY OF THE INVENTION

An exemplary embodiment of the present invention is plasma torch andcomponents thereof that are designed to optimize performance anddurability of the torch. Specifically, exemplary embodiments of thepresent invention can have an improved electrode and cathodeconfiguration.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the invention will be more apparent bydescribing in detail exemplary embodiments of the invention withreference to the accompanying drawings, in which:

FIG. 1 is a diagrammatical representation of an exemplary cutting systemwhich can be used with embodiments of the present invention;

FIG. 2 is a diagrammatical representation of a portion of the head of atorch utilizing known components;

FIGS. 3A and 3B are diagrammatical representations of a portion of thehead of an exemplary embodiment of an aft cooled torch of the presentinvention;

FIGS. 4A and 4B are diagrammatical representations of an exemplaryembodiment of an electrode of the present invention;

FIGS. 5A and 5B are diagrammatical representations of an exemplaryembodiment of a cathode of the present invention;

FIG. 6 is a diagrammatical representation of an exemplary embodiment ofa liquid cooled torch of the present invention;

FIG. 7 is a diagrammatical representation of a magnified view ofcomponents of the torch of FIG. 6;

FIG. 8 is a diagrammatical representation of a thread connection thatcan be used with embodiments of the torch shown in FIG. 6;

FIG. 9 is a diagrammatical representation of the electrode shown in FIG.6;

FIGS. 10A through 10C are a diagrammatical representation of analternative exemplary connection method between an exemplary cathode andelectrode of the present invention; and

FIGS. 11A and 11B are a diagrammatical representation of a furtherexemplary embodiment of a thread connection between an electrode andcathode.

DETAILED DESCRIPTION

Reference will now be made in detail to various and alternativeexemplary embodiments and to the accompanying drawings, with likenumerals representing substantially identical structural elements. Eachexample is provided by way of explanation, and not as a limitation. Infact, it will be apparent to those skilled in the art that modificationsand variations can be made without departing from the scope or spirit ofthe disclosure and claims. For instance, features illustrated ordescribed as part of one embodiment may be used on another embodiment toyield a still further embodiment. Thus, it is intended that the presentdisclosure includes modifications and variations as come within thescope of the appended claims and their equivalents.

The present disclosure is generally directed to plasma arc torchesuseful various cutting, welding and spraying operations. Specifically,embodiments of the present invention are directed to air cooled plasmaarc torches, while others are directed to liquid cooled embodiments. Ofcourse, some of the features described herein can be used in eithertorch configurations without detracting from the novelty of theexemplary embodiments. Further exemplary embodiments are directed to aircooled plasma arc torches which are retract arc torches. As generallyunderstood, retract arc torches are torches where the electrode is incontact with the nozzle for arc initiation and then the electrode isretracted from the nozzle so that the arc is then directed through athroat of the nozzle. In other types of retract torches, the electrodestays stationary and the nozzle is moved. Exemplary embodiments of thepresent invention can apply to both types. The construction andoperation of these torches, as well as liquid cooled torches, aregenerally known, and thus their detailed construction and operation willnot be discussed herein. Further, embodiments of the present inventioncan be used in either handheld or mechanized plasma cutting operations.It should be noted that for purposes of brevity of clarity, thefollowing discussion will be directed to exemplary embodiments of thepresent invention which are primarily directed to a hand held plasmatorch for cutting. However, embodiments of the present invention are notlimited in this regard and embodiments of the present invention can beused in welding and spraying torches without departing from the spiritor scope of the present invention. Various types and sizes of torchesare possible at varying power levels if desired. For example, exemplaryembodiments of the present invention can be used on cutting operationthat utilize a cutting current in the range of 40 to 100 amps, and cancut workpieces having a thickness of up to 0.075 inches, and in otherembodiments can cut workpieces of a thickness of up to 1.5 inches.Further, the torches and components described herein could be used formarking, cutting or metal removal. Additionally, exemplary embodimentsof the present invention, can be used with varying currents and varyingpower levels. The construction and utilization of air coolant systems ofthe type that can be used with embodiments of the present invention areknown and need not be discussed in detail herein.

Turning now to FIG. 1, an exemplary cutting system 100 is shown. Thesystem 100 contains a power supply 10 which includes a housing 12 with aconnected torch assembly 14. Housing 12 includes the variousconventional components for controlling a plasma arc torch, such as apower supply, a plasma starting circuit, air regulators, fuses,transistors, input and output electrical and gas connectors, controllersand circuit boards, etc. Torch assembly 14 is attached to a front side16 of housing. Torch assembly 14 includes within it electricalconnectors to connect an electrode and a nozzle within the torch end 18to electrical connectors within housing 12. Separate electrical pathwaysmay be provided for a pilot arc and a working arc, with switchingelements provided within housing 12. A gas conduit is also presentwithin torch assembly to transfer the gas that becomes the plasma arc tothe torch tip, as will be discussed later. Various user input devices 20such as buttons, switches and/or dials may be provided on housing 12,along with various electrical and gas connectors.

It should be understood that the housing 12 illustrated in FIG. 1 is buta single example of a plasma arc torch device that could employ aspectsof the inventive the concepts disclosed herein. Accordingly, the generaldisclosure and description above should not be considered limiting inany way as to the types or sizes of plasma arc torch devices that couldemploy the disclosed torch elements.

As shown in FIG. 1, torch assembly 14 includes a connector 22 at one endfor attaching to a mating connector 23 of housing 12. When connected insuch way, the various electrical and gas passageways through the hoseportion 24 of torch assembly 14 are connected so as to place therelevant portions of torch 200 in connection with the relevant portionswithin housing 12. The torch 200 shown in FIG. 1 has a connector 201 andis of the handheld type, but as explained above the torch 200 can be ofthe mechanized type. The general construction of the torch 200, such asthe handle, trigger, etc. can be similar to that of known torchconstructions, and need not be described in detail herein. However,within the torch end 18 are the components of the torch 200 thatfacilitate the generation and maintenance of the arc for cuttingpurposes, and some of these components will be discussed in more detailbelow. Specifically, the some of the components discussed below, includethe torch electrode, nozzle, shield and swirl ring.

FIG. 2 depicts the cross-section of an exemplary torch head 200 a of aknown construction. It should be noted that some of the components ofthe torch head 200 a are not shown for clarity. As shown, the torch 200a contains a cathode body 203 to which an electrode 205 is electricallycoupled. The electrode 205 is inserted into an inside cavity of a nozzle213, where the nozzle 213 is seated into a swirl ring 211 which iscoupled to an isolator structure 209 which isolates the swirl ring,nozzle etc. from the cathode body 203. The nozzle 213 is held in placeby the retaining cap assembly 217 a-c. As explained previously, thisconstruction is generally known.

As shown, the electrode 205 has a thread portion 205 a which threads theelectrode 205 into the cathode body 203. The electrode 205 also has acenter helical portion 205 b. The helical portion 205 b has a helicalcoarse thread-like pattern which provides for flow of the air around thesection 205 b. However, because of this section special tooling isrequired to remove the electrode 205 from the cathode body 203.Downstream of the center portion 205 b is a cylindrical portion 205 c,which extends to the distal end 205 d of the electrode 205. As shown,the cylindrical portion is inserted into the nozzle 213, such that thedistal end 205 d is close to the throat 213 b of the nozzle 213. Thecylindrical portion can include a flat surface at the center portion 205b so that a specialized tool can grab the electrode 205 to remove itfrom the cathode. Typically, the transition from the cylindrical portion205 c to the distal end 205 d includes a curved edge leading a flat endface on the distal end 205 d. In a retract start torch this flat endface is in contact with the inner surface of the nozzle 213 to initiatethe arc start. Once the arc is ignited the electrode 205 is retractedand a gap is created between the electrode 205 and the nozzle 213 (asshown), at which time the plasma jet is directed through the throat 213b of the nozzle 213 to the workpiece. It is generally understood, thatwith this configuration, known electrodes 205 can begin to fail duringarc initiation after about 300 arc starts. Typically, the electrode 205is chrome or nickel plated to aid in increasing the life of theelectrode 205. Once this event begins to occur, the electrode 205 mayneed to be replaced.

Also, as shown a hafnium insert 207 is inserted into the distal end 205d of the electrode 205. It is generally known that the plasma jet/arcinitiates from this hafnium insert 207, which is centered on the flatsurface of the distal end 205 d.

As briefly explained above, the torch 200 a also includes a nozzle 213which has a throat 213 b threw which the plasma jet is directed duringcutting. Also, as shown the nozzle 213 contains a cylindrical projectionportion 213 a through which the throat 213 b extends. This projectionportion 213 a provides for a relatively long throat 213 b and extendsinto an cylindrical opening in the shield 215, which also has acylindrical projection portion 215 a. As shown, and air flow gap iscreated between each of the projection portions 213 a/215 a to allow ashielding gas to be directed to encircled the plasma jet during cutting.In air cooled torches, each of these respective projection portions 213a/215 a direct the plasma jet and shield gas to the getting operation.However, because of the geometry of each of the nozzle 213 and theshield cap 215, these projection portions can tend to heat upsignificantly. This heat can cause the heat band on the nozzle 213 toextend significantly along its length. This increased heat band and highheat can cause the components to deteriorate and fail, causing the needfor replacement. Further, their performance can degrade over time whichcan cause less than optimal cutting results. Therefore, improvements areneeded for known air cooled torch configurations.

Turning now to FIGS. 3A and 3B, an exemplary embodiment of a torch 300is shown. The torch 300 can be used in the torch 200 shown in FIG. 1,and like FIG. 2, not all of the components and structure is shown tosimplify the Figure (for example, handle, outer casing, etc.). Further,in many respects (except those discussed below) the construction andoperation of the torch 300 is similar to known torches, such that all ofthe details of its construction need not be discussed herein. However,as will be explained in more detail below, some of the components of thetorch 300 are constructed differently than known torches and torchcomponents and provide for a cutting torch with optimized cuttingperformance and durability. Further, like the torch 200 a in FIG. 2, thetorch 300 in FIG. 3 is an air cooled, retract-type torch. Furtherunderstanding of exemplary embodiments of the present invention isprovided in the discussions below, in which some of the components arediscussed.

As shown in each of FIGS. 3A and 3B, the torch 300 has a torch body 301and a torch head 300′. This is a known construction methodology, wherethe torch head 300′ can be secured to the torch body 301 via aconnection mechanism. As shown, the torch body has a parts in placeswitching mechanism 309 which makes contact with a brass ring 308. Thisconnection completes an electrical circuit which then indicates to thesystem 100 that the torch head 300′ is properly secured to the torchbody 301. In other exemplary embodiments the parts-in-place sensing canbe done by a sealed switch actuated by a plunger, or other similarswitch construction which indicates that the components are properlysecured to each other. Like the torch shown in FIG. 2, the torch head300′ includes an electrode 305, swirl ring 311, shield cap 315, anode307, cathode 303, nozzle 314 and an isolator 312. Also included is abias member 313, such as a spring. FIG. 3A depicts the torch in an arcignition/pilot arc mode where the distal tip of the electrode 305 is incontact with the nozzle 314. The bias member 313 holds the electrode 305and cathode 303 (to which the electrode is coupled) in this positioncreating the gap G between the isolator 312 and the cathode 303 asshown. This contact between the nozzle 314 and the electrode 305 allowsan arc to be ignited when current is first applied to the torch 300. Atthe same time a gas pressure is provided to the torch which causes theelectrode/cathode to retract away from the nozzle 314. This position isshown in FIG. 3B which shows the gap G reduced to allow contact betweenthe cathode 303 and the isolator 312, as the bias member 313 iscompressed. Also a gap is created between the electrode tip and thenozzle 314 such that the created arc is transferred to the work piece toallow the cutting to begin. This movement of the electrode/cathode istriggered by the influx of a gas/air pressure which pushes theelectrode/cathode assembly against the bias member 313. In addition toproviding the pressure to electrode/cathode the gas/air flow also aidsin cooling the components as it passes over the surfaces of thesecomponents. To aid in the cooling, channels/grooves are placed on theouter surface of the electrode/cathode. However, as the cooling gas/airpasses over the surface of these components it can impart undesiredforces on the components because of the grooves. For example, the flowcan be directed such that it imparts an undesired torsional force on theelectrode/cathode. Further, the flow can be directed such that itimparts uneven forces on the components. These torsional/uneven forcescan compromise the operation efficiencies of torches and adverselyaffect cutting operations and/or decrease the operation life ofcomponents. As discussed below, embodiments of the present inventionaddress these concerns.

FIGS. 4A and 4B depict an exemplary embodiment of the electrode 305 usedin the torch 305. The electrode 305 has a distal end 305′ which isinserted into the nozzle and at the end face of which a hafnium insert306 is inserted—from which the arc originates. Of course, anothermaterial can be used besides hafnium. In exemplary embodiments, theelectrode 305 can be made from copper or a copper alloy, or othersuitable materials. Upstream of the distal end 305′ is a shoulderportion 320 which has a maximum outer diameter which is in the range of55 to 65% larger in diameter than the maximum outer diameter of thedistal end portion 305′. In some exemplary embodiments, the shoulderportion 320 has the maximum outer diameter of the entire electrode 305.Upstream of the shoulder portion 320 is a transition portion 321 havingan angled surface 321′ (which angles toward the centerline of theelectrode 305 as it travels upstream) and a non-angled surface 321″which is parallel to the centerline of the electrode 305. Upstream ofthe transition portion 321 is a central groove portion 305″. Inexemplary embodiments, the central groove portion 305″ has a two-threadfeature, where the threads are in the range of 130 to 180 degrees apart.In an exemplary embodiment, the threads are 150 degrees apart. As shown,the threads have grooves 322 and crests 323 and 324. In the exemplaryembodiment shown, a first crest 323 has a first crest width and a secondcrest 324 has a second crest width which is wider than the first crestwidth. In exemplary embodiments, the second crest width is in the rangeof 1.5 to 3 times the width of the first crest width. In other exemplaryembodiments, the second crest width is in the range of 2 to 2.5 timesthe first crest width. Further, in additional exemplary embodiments, themaximum outer diameter of the groove portion 305″ is the same as themaximum outer diameter of the shoulder portion 320. As shown, inexemplary embodiments, the first and second crests alternate whichrespect to each other such that no two first or second crests areadjacent to each other. Further, as shown in FIG. 4B, the grooves 322are configured such that the groove surfaces 327 are angled to create anangle A between adjacent groove surfaces 327. In exemplary embodiments,the angle A is in the range of 20 to 40 degrees. In other exemplaryembodiments, the angle A is in the range of 26 to 32 degrees. Inexemplary embodiments, the grooves 322 have a depth X (from the creststo the roots) which is in the range of 4 to 10% of the maximum outerdiameter of the groove portion 305″. Further, in exemplary embodiments,the grooves are configured such that they are in the range of 4 to 8 TPI(turns per inch). In other exemplary embodiments, the electrode grooveshave 5 to 7 TPI, and yet in further embodiments, the grooves have 6 TPI.The grooves can be configured as a right hand thread or a left handthread.

Upstream of the groove portion 305″ is an angled transition portion 325,followed by a shoulder portion 326 and an upstream end portion 305′″. Atleast a portion of the upstream end portion is inserted into anelectrode cavity of the cathode 303, as shown in FIGS. 3A and 3B. Theangled portion 325 is angled relative to the centerline CL such that thesurface angle is in the range of 40 to 50 degrees relative to thecenterline. In other exemplary embodiments, surface of the angledsurface 325 is 45 degrees relative to the centerline CL. In exemplaryembodiments, the upstream end portion 305′″ has a maximum outer diameterwhich is smaller than the maximum outer diameter of the distal endportion 305′.

In exemplary embodiments, this electrode/groove configuration canprovide optimal air/gas flow for cooling and to provide the desiredupward pressure forces to ensure proper operation of the torch 300.However, because of the spiral nature of the grooves as shown, asdescribed above, a torsional force can be imparted on the electrode 305,trying to turn the electrode 305 relative to its centerline CL. Thistorsional force is counteracted by the configuration of the cathodedescribed below. Of course, it should be noted that the overallappearance, geometrical shape, etc. of the electrode can be changed tofit the desired torch configuration and have the desired appearancewithout departing from the spirit or scope of the embodiments of theinvention described above, and the views shown in the figures describedherein are intended to show one exemplary embodiment.

FIGS. 5A and 5B depict an exemplary embodiment of the cathode 303 shownin FIGS. 3A and 3B. The cathode 303 has a distal end 331 into which acavity is created (shown in FIGS. 3A/3B) to allow for the insertion ofthe upstream end 305′″ of the electrode 305. The cavity is configuredsuch that a contact fit is made between the electrode 305 and thecathode cavity. Adjacent to the distal end face 331 is a shoulderportion 332 and a separator portion 333. The separator portion separatesthe shoulder portion 332 from the groove portion 303′. As shown, thegroove portion 303′ has a spiral groove 335 extending along its length.In exemplary embodiments, the spiral groove 335 is different than thegrooves on the electrode. For example, in exemplary embodiments, thegroove 335 is a single groove, unlike the double groove/thread featureof the electrode 305. Further, as shown, in exemplary embodiments, themaximum outer diameter of the groove crests 334 is the maximum outerdiameter of the cathode 303. However, in some embodiments, the maximumouter diameter of the cathode—at the crests 334—is less than the maximumouter diameter of the electrode 305. Additionally, in exemplaryembodiments, the groove 335 creates crests 334 which do not alternate insize—that is the width of the crest 334 is consistent throughout thegroove portion 303′. Additionally, while the groove 335 can be either aleft or right hand groove, the spiraling should be opposite of that ofthe electrode groove(s). For example, if the electrode groove(s) is aright hand thread, the groove 335 of the cathode should be a left handthread. This ensures that the torsional forces from the air/gas flowalong the electrode are counteracted by the subsequent flow along thecathode 303. By changing thread directions, the air/gas flow providesstructural stabilization that would not otherwise be achieved. Further,the groove 335 of the cathode 303 is to have a different TPI than thatof the groove(s) used on the electrode. For example, in exemplaryembodiments, the groove 335 of the cathode 303 has a higher thread countthan that of the electrode. In exemplary embodiments, the groove 334 hasa thread count in the range of 7 to 12 TPI, and is higher than that ofthe electrode. In further exemplary embodiments, the thread count is inthe range of 8 to 10 TPI. In even further exemplary embodiments, thethread count of the cathode is at least 3 TPI higher than that of thethread count on the electrode 305. For example, Of course, in otherexemplary embodiments, the thread count of the electrode groove(s) is 6TPI the thread count of the groove 335 is at least 9 TPI.

Upstream of the groove 335 is a collar portion 336 which couples thegroove portion to a shoulder portion 337. In an exemplary embodiment,the collar portion 336 has a smaller outside maximum diameter which issmaller than the outside diameter of the separator portion 333. Theshoulder portion 337 has a maximum outside diameter, which in someembodiments is the same as the outside diameter of the shoulder portion332. Upstream of the shoulder portion 337 is another collar portion 338which couples the shoulder portion 337 to an additional shoulder portion339. In exemplary embodiments, the collar portion 338 has a maximumouter diameter that is larger than the outer diameter of the portion336. Upstream of the shoulder portion 339 is a cylindrical portion 340which has a maximum outside diameter. In exemplary embodiments, theoutside diameter of the cylindrical portion 340 is smaller than theoutside diameters of each of the collar portions 338, 336 and separatorportion 333. Upstream of the cylindrical portion is a groove 341 and anextension portion 342.

FIG. 5B shows a cross-section of the groove 335, similar to that in FIG.4B. As shown, the groove surfaces 343 are angled such that an angle B isformed between them. In exemplary embodiments, the angle B is in therange of 20 to 40 degrees. In other exemplary embodiments, the angle Bis in the range of 26 to 32 degrees. In further embodiments, the angle Bis the same as the angle A on the electrode. In exemplary embodiments,the grooves 335 have a depth Y (from the crests to the roots) which isin the range of 6 to 12% of the maximum outer diameter of the grooveportion 303′. In further exemplary embodiments, the groove 335 has adepth Y which is greater than the depth X of the groove(s) on theelectrode 305. For example, in exemplary embodiments, the groove depth Yis in the range of 15 to 30% larger than the depth X. In additionalexemplary embodiments, the depth Y is in the range of 20 to 25% largerthan the depth X.

With the above described relationships between the spiral grooves oneach of the electrode 305 and the cathode 303 the utilization of the airflow along the electrode 305 and cathode 303 is optimized, whileavoiding imparting unnecessary forces on the components. Specifically,the flow channels are changed such that the flow does not maintain asmooth laminar flow, but has to change directions between the componentsand its flow is different along each components because of thedimensional differences. Further, in exemplary embodiments because ofthe varying respective lengths of the groove portions of each respectivecomponent the differing dimensional relationships allow the torsionalforces on each respective component to balance out, or come close tobalancing out, while at the same time allowing for optimal pressureperformance of the air/gas flow to move the electrode/cathode assemblyas needed to transition from arc strike to arc transition/cutting. Forexample, the overall length L′ of the spiral groove 335 (along thelength of the cathode) is in the range of 20 to 35% of the overalllength of the cathode 303 (from end to end). In further exemplaryembodiments, the length L′ is in the range of 25 to 30% of the overalllength. However, on the electrode 305 the length L of the spiral grooves(along the axis of the electrode) is in the range of 30 to 40% of theoverall length of the electrode 305. In other exemplary embodiments, thelength L is in the range of 35 to 40% of the overall length of theelectrode 305. In some exemplary embodiments the lengths L and L′ arethe same, while in other exemplary embodiments, the length L is longerthan L′.

With the above electrode 305 and cathode 303 physical relationships anddescribed attributes, exemplary embodiments of the present inventionallow for an air cooled, retract type torch to have an optimizedperformance.

Turning now to FIG. 6, an exemplary embodiment of a liquid cooled torch600 is depicted. In general, the torch 600 is constructed consistentwith similar known liquid cooled torches. For example, the torchincludes a nozzle 613, shield cap 611, nozzle retaining cap 609,electrode 601, cathode 603, outer cap 605 and outer casing 607. Ofcourse, the torch 600 includes other components that need not bediscussed herein. However, as shown in FIG. 6, and further discussedbelow, the threaded connections between components use a novel threadconfiguration, which is discussed in more detail below.

The thread configuration utilized by embodiments herein is a modifiedstub ACME thread design. An ACME thread design is known by those ofskill in the art and need not be described in detail herein, and itsdescription can be found in the Machinery's Handbook; Oberg, Jones, andHorton, Industrial Press, Inc.; 1979, the ACME stub thread designsection is incorporated herein by reference in its entirety.

A closer view of exemplary thread configurations is shown in FIGS. 7 and8. As shown, a modified ACME stud thread configuration is used to jointhe electrode 601 to the cathode 603. It should be noted that while thisthread configuration is discussed in reference to the electrode/cathodeconnection. This thread configuration can be used elsewhere as well—asshown in FIG. 6. For example, the nozzle retaining cap 609 and/or theouter cap 605 can use the described thread configurations to aid inproviding an optimal connection. This modified ACME stud threadconfiguration is used by embodiments of the present invention toincrease the concentricity of torch components when the torch isassembled. Because of the need for high levels of concentricity toensure optimum torch performance and life, it is often very difficult tomanufacture components with the needed high level of precision to ensurethis concentricity. Therefore, there is a need for threaded connectionswhich are easy to manufacture, provide a high level of concentricitywhen assembled and provide a large contact surface for electrical andthermal conductivity. Embodiments of the present accomplish this withthe configurations discussed below.

Turning now to FIGS. 7 and 8, the cathode 603 has a female thread 603′while the electrode has a male thread 601′. In exemplary embodiments ofthe present invention, in each of the male and female threads the crestwidth of the threads is larger than the root width of the threads. Thisis not consistent with many known thread configurations. Further, inadditional exemplary embodiments, the crest width, in each of the maleand female threads, is in the range of 1 to 5% larger than that of theroot width, in each of the respective male and female threads. Infurther exemplary embodiments, the crest width is 2 to 3.5% larger thanthat of the root width, and in additional exemplary embodiments, thecrest width is in the range of 2.5% to 3.5 larger than that of the rootwidth. Of course, these ratios are for a thread formation with arelatively small included angle—for example, a 10 degree included angle.

In exemplary embodiments, the included angle between the sidewalls ofthe threads φ is in the range of 10 to 60 degrees. However, in otherexemplary embodiments, the included angle φ is 10 degrees. With such asteep angle the threads are practically square threads and can provide ahigh level of concentricity and strength.

Further, the threads are configured such that the gap G1 (which is theclearance between the minor diameter of the male thread 601′ and theminor diameter of the female thread 603′) is smaller than the gap G2(which is the clearance between the major diameter of the male thread601′ and the major diameter of the female thread 603′). In exemplaryembodiments, this clearance relationship with the above discussedconfiguration provides a thread configuration which is relatively easyto manufacture and easy to secure to each other (preventingcross-stripping) and also provides a high level of concentricity andcontact between components.

In exemplary embodiments, the threads have a pitch such that they are inthe range of 10 to 14 TPI. In further exemplary embodiments, the threadhas a pitch of 12 TPI. It should be noted that due to geometrical andtooling limitations, the pitch used can affect the relationship betweenthe crest and root sizes.

FIGS. 11A and 11B depict a further exemplary embodiment of the presentinvention, where a modified square thread pattern is used similar tothat described above. However, in this exemplary embodiment therelationship between the roots and crests of the threads of theelectrode and cathode have an opposite relationship. Specifically, inthis exemplary embodiment the male threads of the electrode have a crestwidth Xc which is larger than the male thread root width Yr. Inexemplary embodiments the included angle φ is 10 degrees, while in otherembodiments the included angle can be different, such as in the range of10 to 40 degrees. In exemplary embodiments, the ratio between the crestwidth Xc and root width Yr is in the range of 1.2 to 1.6. In furtherexemplary embodiments, the ratio is in the range of 1.35 to 1.45.However, with these exemplary embodiments, the female threads of thecathode 603 have a crest width Xc′ which is smaller than the root widthYr′. This is the opposite of the size relationship on the electrode. Inexemplary embodiments, for the cathode thread the ratio between thecrest width Xc′ and root width Yr′ is in the range of 0.5 to 0.75. Infurther exemplary embodiments, the ratio is in the range of 0.65 to 0.7.Like the male thread, the included angle on the female threads of thecathode can be in the range of 10 to 40 degrees, while in someembodiments the included angle φ is 10 degrees. The thread count inexemplary embodiments can be in the range of 12 to 16 TPI, and infurther exemplary embodiments the thread count is 12 TPI. Like theexemplary configurations discussed above, this exemplary configurationallows for improved alignment, physical and electrical connectionbetween components, ease of installation between the components, andconcentricity of components.

This concentricity improvement is enhanced through the use of the dualo-ring configuration as shown in FIGS. 6 and 7. As shown, two o-rings621 and 622 are positioned downstream of the thread portion of theelectrode 601. The use of two o-rings with the above threadconfiguration improves concentricity of the electrode 601. The abovedescribed thread configuration allows the o-rings 621/622 to provide anincreased role in positioning the electrode over known configurations.That is, in known configurations, the threads were the primary driver inpositioning the electrode 601. As such, if the threads were manufacturedpoorly and/or were stripped during installation the concentricity of thecomponents would be adversely affected. However, in current exemplaryembodiments, the threads allow the o-rings 621/622 to have an increasedrole in ensuring that the electrode is positioned centrally. This is dueto the compressibility of the o-rings, which tend to compress evenlyaround the perimeter of the electrode 601. Thus, the above describedconfiguration of the electrode, and its coupling allows the electrode601 to be centralized in the torch and in the isolator—as shown in FIG.6.

FIG. 9 depicts an exemplary cross-section of the exemplary electrode601. The electrode 601 has an upstream end 631 with an opening for thecooling cavity 637, and a distal end 633 with an opening 635 for aninsert, which can be a hafnium insert or the like. The electrode has athread portion 601′ as described above. Downstream of the thread portion601′ is a shoulder 632 which separates the thread portion 601′ from theo-ring portion 639. The o-ring portion 639 has at least two o-ringgrooves 621′ and 622′. Additionally, in exemplary embodiments, theo-ring portion 639 and o-ring grooves 621′ and 622′ are positioned suchthat the distance D along the length of the electrode 601, as measuredfrom the upstream end 631 to the center of the first groove 622′, is inthe range of 20 to 25% of the overall length of the electrode (fromupstream end 631 to the distal end 633). Additionally, the distance D′between the centers of each of the respective grooves 621′ and 622′ isin the range of 5 to 10% of the overall length of the electrode 601.This geometry, coupled with the above described thread configurationallows the electrode 601 to be easily installed having a high level ofconcentricity in the torch 600.

FIGS. 10A through 10C depict a further exemplary embodiment of thepresent invention. As shown in these Figures, an additional threadedconnection is shown. However, in this embodiment, the threadedconnection has a first threaded section 901 and a second threadedsection, where the sections use different thread configurations. Thisconfiguration utilizes two different threaded connections to provide asecure connection between the electrode 601 and the cathode body 603.Like the connections discussed above, this type of configuration alsoprovides improved concentricity while ensuring a secure fitment betweencomponents. Additionally, such a connection configuration increases thedurability and connectivity of the coupling between components. Furtherdetail is shown in FIGS. 10B and 10C. It is noted that the electrode andcathode shown in these figures can have a similar overall configurationand function of the other embodiments, described herein. For example,the electrode 601 can have a distal end with an emissive insert (e.g.,hafnium), as shown in FIG. 9.

FIG. 10B depicts an exemplary cathode body 603 (only the distal endportion is shown) and FIG. 10C depicts an exemplary upstream end of theelectrode 601. Each of the first and second threaded sections 901/903have a single spiral thread. However, the threads in each respectivesection are different. For example, the threads-per-inch in each of therespective sections is different. As an example, in some embodiments thefirst section 901 has a thread within the range of 20 to 28 TPI, and thesecond section 903 has a thread within the range of 16 to 24 TPI, wherethe thread of the second section 903 has a smaller TPI than the firstsection 901. In an exemplary embodiment, the first section 901 has 24TPI, while the second section has 20 TPI. The pitch and TPI of therespective threads should be selected to ensure smooth engagement of therespective threads in each respective section. If this is not achieved,it could result in binding when installing the electrode 601 within thecathode body.

Further, while in some exemplary embodiments, the thread cross-sectionalgeometry can be the same, in other embodiments, the respective threadscan have different cross-section geometries. For example, in exemplaryembodiments, the thread of the first section 901 can have a large depth(from crest to root) than the thread of the second section 903. Further,in additional exemplary embodiments the root widths of the respectivethreads can be different. In the embodiment shown, the threads in eachof the sections have a truncated cone cross-section so that therespective crests and roots do not have a sharp point and this a stressconcentration.

Further, as shown, the first section 901 has a smaller diameter than thesecond section 903. On the cathode body 603, each of the respectivesections have a major and minor diameter, for each of the respectivecomponents, as shown in FIGS. 10B and 10C. In exemplary embodiments ofthe present invention, in the cathode 603, the major diameter of thefirst section DM1 has a smaller diameter (as measured across thecross-section of the cathode) than the minor diameter of the secondsection Dm2. In some exemplary embodiments, the major diameter of thefirst section DM1 has the same diameter as the minor diameter of thesecond section Dm2. Similarly, with respect to the electrode 601, inexemplary embodiments the major diameter of the first section DM1′ has asmaller diameter than the minor diameter of the second section Dm2′. Insome exemplary embodiments, the minor diameter of the second sections,in each of the electrode and cathode, is in the range of 2 to 6% largerthan the major diameter in each of their respective first sections. Infurther exemplary embodiments, the minor diameter of the secondsections, in each of the electrode and cathode, is in the range of 3 to5% larger than the major diameter in each of the respective firstsections. For purposes of reference, Dm1 is the minor diameter of thefirst section of the cathode, DM2 is the major diameter of the secondsection of the cathode, Dm1′ is the minor diameter of the first sectionof the electrode, and DM2′ is the major diameter of the second sectionof the electrode. These can be dictated by the selected depths of thethreads used in each respective sections.

In other exemplary embodiments, a combination of the above discussedmodified square thread and a true square thread profile is utilized onadjoining male/female thread components. In a true square threadconfiguration, the included angle φ (discussed above, see for exampleFIG. 8) of the thread is in the range of 0 to 1 degrees. That is, thecross-section of the thread at the transition from the crest to wall orfrom the root to the thread wall is a right angle, or nearly a rightangle. In other exemplary embodiments, the included angle is 0 degrees,such that the root to wall and/or crest to wall transition is a rightangle. That is, in exemplary embodiments, some of the threadedconnections discussed herein can have female threads with the includedangles and geometry discussed previously, while the corresponding malethreads have the square shape. In other exemplary embodiments, theopposite is true, where the male threads have the geometrycharacteristics discussed above, while the corresponding female threadsare square. In either of the these embodiments, the root to crestrelationships discussed above can be maintained to achieve the benefitsdescribed above. In other exemplary embodiments utilizing the nearsquare thread configuration, the included angle is in the range of 0 to4 degrees, and even further embodiments, the included angle for thenearly square thread is in the range of 0 to 10 degrees. In even furtherembodiments, the near square thread has an included angle in the rangeof 1 to 8 degrees.

This alternative relationship can be utilized on many of the connectionsdiscussed above using the described modified thread connectionsdescribed herein. In certain exemplary embodiments, the use of thecombined square and modified square threads can provide improved ease ofconnectability, as the overall contact surface area is reduced. However,it should be noted that, in some embodiments, this type of mated threadconfiguration would not be desirable for high current flow applications.That is, if high current is passed through the threads (for example, theelectrode/electrode holder connection) then this thread configurationmay cause high heat/current concentrations at the thread contact points.Thus, in some exemplary embodiments, these combined thread configurationis used in applications having a maximum current flow at or below 150amps. In other exemplary embodiments, this configuration is used inembodiments, where the maximum current flow is at or below 65 amps. Infurther exemplary embodiments, this thread connection methodology isused for only purely mechanical connections, which have no current flow.In referring to at least FIG. 6, the above described connection can beused for the connection of the cap 605, the nozzle retaining cap 609,and the electrode 601, as examples.

While the subject matter of the present application has been describedwith reference to certain embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted without departing from the scope of the subject matter.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the subject matter withoutdeparting from its scope. Therefore, it is intended that the subjectmatter not be limited to the particular embodiment disclosed, but thatthe subject matter will include all embodiments falling within the scopedescribed herein.

I claim:
 1. A plasma cutting electrode, said electrode comprising: adistal end having an emissive insert inserted therein, where said distalend is insertable into a nozzle of a plasma cutting torch, said distalend having a first outer diameter; a shoulder portion upstream of saiddistal end, said shoulder portion having a second outer diameter whichis larger than said first outer diameter; a central groove portionupstream of said shoulder portion, said central groove portion having afirst thread with a first crest width and a second thread with a secondcrest width which is in the range of 1.5 to 3 times larger than thefirst crest width and each of said first and second threads have agroove, respectively, where each of said grooves have angled sidewalls,and where said central groove portion has a third outside diameter; andan upstream end portion, upstream of said central groove portion, wheresaid upstream end portion has a fourth outside diameter.
 2. Theelectrode of claim 1, wherein said second outer diameter is in the rangeof 55 to 65% larger than said first outer diameter.
 3. The electrode ofclaim 1, wherein said second crest width is in the range of 2 to 2.5times larger than said first width.
 4. The electrode of claim 1, whereinsaid third outside diameter is the same as said second outside diameter.5. The electrode of claim 1, wherein an included angle between thesidewalls of each respective groove is in the range of 20 to 40 degrees.6. The electrode of claim 1, wherein each of said grooves have a depthwhich is in the range of said 4 to 10% of the third outside diameter. 7.The electrode of claim 1, wherein each of said first and second threadsare in the range of 4 to 8 turns per inch.
 8. A plasma cutting torch,comprising: a cathode having a cavity portion with an opening on adistal end of said cathode portion; an electrode partially inserted intosaid cavity portion of said cathode, said electrode comprising: a distalend having an emissive insert inserted therein, said distal end having afirst outer diameter; a shoulder portion upstream of said distal end,said shoulder portion having a second outer diameter which is largerthan said first outer diameter; a central groove portion upstream ofsaid shoulder portion, said central groove portion having a first threadwith a first crest width and a second thread with a second crest widthwhich is in the range of 1.5 to 3 times larger than the first crestwidth and each of said first and second threads have a groove,respectively, where each of said grooves have angled sidewalls, andwhere said central groove portion has a third outside diameter; and anupstream end portion, upstream of said central groove portion, wheresaid upstream end portion has a fourth outside diameter; and a nozzle,into which said distal end of said electrode is inserted; wherein saidcathode has a thread on an outer portion of said cathode and said threadis oriented in an opposite direction of an orientation of said first andsecond threads on said electrode.
 9. An electrode for a plasma cuttingtorch, said electrode comprising: a distal end portion having a cavityinto which an emissive insert is inserted; a body portion upstream ofsaid distal end portion, said body portion having a cooling cavity wheresaid cooling cavity is open at an upstream end of said electrode; and athread portion positioned on an outer surface of said body portion andadjacent to said upstream end of said electrode, where said threadportion comprises a male thread which has a crest with a crest width anda root with a root width, where said crest width has a width which is inthe range of 1 to 5% larger than said root width, and where said malethread has angled sidewalls between said root and said crest, where saidangled sidewalls have an included angle in the range of 10 to 60degrees; wherein said crest of said thread has a height which creates afirst gap between said crest and a corresponding root on an engagingfemale thread and said root has a depth which creates a second gapbetween said root and a corresponding crest on said engaging femalethread, where said first gap is larger than said second gap.
 10. Theelectrode of claim 9, wherein said crest width is in the range of 2 to3.5% larger than said root width.
 11. The electrode of claim 9, whereinsaid included angle is 10 degrees.
 12. The electrode of claim 9, whereinsaid thread has between 10 to 14 turns per inch.
 13. The electrode ofclaim 9, wherein said thread has 12 turns per inch.
 14. An electrode fora plasma cutting torch, said electrode comprising: a distal end portionhaving a cavity into which an emissive insert is inserted; a bodyportion upstream of said distal end portion, said body portion having acooling cavity where said cooling cavity is open at an upstream end ofsaid electrode; and a thread portion positioned on an outer surface ofsaid body portion and adjacent to said upstream end of said electrode,where said thread portion comprises a male thread which has a crest witha crest width and a root with a root width, wherein a ratio between saidcrest width and said root width is in the range of 1.2 to 1.6, and wheresaid male thread has angled sidewalls between said root and said crest,where said angled sidewalls have an included angle in the range of 10 to40 degrees; wherein said crest of said thread has a height which createsa first gap between said crest and a corresponding root on an engagingfemale thread and said root has a depth which creates a second gapbetween said root and a corresponding crest on said engaging femalethread, where said first gap is larger than said second gap.
 15. Theelectrode of claim 14, wherein said ratio is in the range of 1.35 to1.45.
 16. The electrode of claim 14, wherein said included angle is 10degrees.
 17. The electrode of claim 14, wherein said thread has between12 to 16 turns per inch.
 18. A plasma cutting torch, comprising: anelectrode, said electrode comprising: a distal end portion having acavity into which an emissive insert is inserted; a body portionupstream of said distal end portion, said body portion having a coolingcavity where said cooling cavity is open at an upstream end of saidelectrode; and a thread portion positioned on an outer surface of saidbody portion and adjacent to said upstream end of said electrode, wheresaid thread portion comprises a male thread which has a crest with acrest width and a root with a root width, wherein a ratio between saidcrest width and said root width is in the range of 1.2 to 1.6, and wheresaid male thread has angled sidewalls between said root and said crest,where said angled sidewalls have an included angle in the range of 10 to40 degrees; and a cathode body having a cavity into which at least aportion of said electrode is inserted, said cavity having a femalethread which engages with said male thread, where said female thread hasa crest with a crest width and a root with a root width, and where saidfemale thread has angled sidewalls between said female thread crest andsaid female thread root, where said angled sidewalls have an includedangle in the range of 10 to 40 degrees; wherein said crest width of saidfemale thread is smaller than a root width of said female thread. 19.The plasma torch of claim 18, wherein a ration between said femalethread crest width and said female thread root width is in the range of0.5 to 0.75.
 20. The plasma torch of claim 18, wherein said ratio is inthe range of 1.35 to 1.45.
 21. An electrode for a plasma torch,comprising: a distal end having an emissive insert inserted therein,where said distal end is insertable into a nozzle of a plasma cuttingtorch, said distal end having a first outer diameter; and an upstreamend portion which is insertable into a cathode, where said upstream endportion has a first threaded portion closest to said upstream end ofsaid electrode and a second threaded portion positioned downstream ofsaid first threaded portion, wherein said first threaded portion has afirst thread have a first thread pitch and a first major diameter and afirst minor diameter, and wherein said second threaded portion has asecond thread with a second thread pitch and a second major diameter anda second minor diameter, where said second major diameter is larger thansaid first major diameter.
 22. The electrode of claim 21, wherein saidfirst thread pitch is in the range of 20 to 28 threads per inch and thesecond thread pitch is in the range of 16 to 24 threads per inch, wheresaid second thread pitch is smaller than said first thread pitch. 23.The electrode of claim 21, wherein said second minor diameter is largerthan said first major diameter.
 24. The electrode of claim 23, whereinsaid second minor diameter is in the range of 2 to 6% larger than saidfirst major diameter.
 25. The electrode of claim 23, wherein said secondminor diameter is in the range of 3 to 5% larger than said first majordiameter.